Vacuum IG (VIG) units are known in the art. For example, see U.S. Pat. Nos. 5,664,395, 5,657,607, 6,399,169, 6,641,689, 6,692,600 and 5,902,652, the disclosures of which are all hereby incorporated herein by reference.
Prior art FIGS. 1-2 illustrate a conventional vacuum IG unit. IG unit 1 includes two spaced apart sheets of glass 2 and 3 which enclose an evacuated or low pressure space 6 therebetween. Glass sheets 2 and 3 are interconnected by peripheral or edge seal of fused solder glass 4 and an array of support pillars or spacers 5.
Pump out tube 8 is sealed by solder glass 9 to an aperture or hole 10 which passes from an interior surface of glass sheet 2 to the bottom of recess 11. A vacuum is attached to tube 8 so that the cavity between sheets 2 and 3 can be evacuated to create a low pressure area 6 between the opposing glass substrates. After evacuation, tube 8 is melted to seal the vacuum. Recess 11 retains melted and sealed tube 8. Chemical getter 12 may be included within machined recess 13. Alternatively, although not shown, the pump-out tube or hole may be located in the edge seal instead of in one of the glass substrates 2, 3.
In prior art FIGS. 1-2, edge seal 4 is made entirely from solder glass. For example, see U.S. Pat. No. 5,902,652. As explained in the '652 patent, the solder glass edge seal is formed by depositing the solder glass as a liquid slurry onto the surface of one or both of the glass sheets 2, 3. The glass sheets 2 and 3 are then brought together and the entire unit is then heated to a temperature at which the solder glass melts, wets the surface of the glass sheets, and flows to produce a hermetic edge seal 4 between the glass sheets 2 and 3.
Unfortunately, the edge seal 4 of FIGS. 1-2, made entirely of solder glass and directly contacting both glass substrates, is disadvantageous in certain situations. During many environmental conditions in which the VIG unit may be used (e.g., during hot, cold, and/or windy conditions), there tends to be much flexing of the vacuum IG window unit. The nature of the edge seal 4 in FIGS. 1-2 causes such flexing to distort the optics of the window unit, and breakage of the window unit is even possible in extreme conditions.
It is apparent from the above that there exists a need in the art for a vacuum IG unit, and corresponding method of making the same, including an improved edge seal between opposing glass sheets or substrates.
This invention will now be described with respect to certain embodiments thereof, accompanied by certain illustrations.